Backside Reflection Optical Display

ABSTRACT

The disclosure generally involves an optical (perhaps flat panel) display utilizing backside reflection for time-multiplexed optical shuttering. One display comprises a side-illuminated light guide associated with conditions for total internal reflection. A first surface of the light guide is elastomeric. Disposed against this elastomeric surface is an active layer that selectively deforms the elastomeric surface in locations that can correspond to display pixels. This resulting change in the geometry of the elastomeric surface can be sufficient to defeat the conditions for total internal reflection. When appropriate, light is reflected by the particular deformation and is ejected from another surface of the light guide. In this case, each location that allows light to exit could represent an activated display pixel. In certain situations, color flat panel displays of varying sizes may further implement field sequential color and time-multiplexed optical shuttering.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. patent application Ser. No.11/524,704, filed Sep. 21, 2006, entitled “BACKSIDE REFLECTION OPTICALDISPLAY,” and issued Jul. 6, 2010 as U.S. Pat. No. 7,751,663, thedisclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to the field of display devicesand, more particularly, to an optical (perhaps flat panel) displayutilizing backside reflection.

BACKGROUND OF THE INVENTION

Certain flat panel displays exploit the principle of frustrated totalinternal reflection (FTIR) to induce the emission of light from therespective system. Such displays may be achieved through the utilizationof microelectromechanical systems or nanoelectromechanical systems(often collectively referred to as MEMS). For example, onerepresentative of FTIR-based MEMS devices may be a time multiplexedoptical shuttering (TMOS) display. These TMOS devices may each begenerally able to selectively frustrate the light undergoing totalinternal reflection within a (generally) planar waveguide. When suchfrustration occurs, the selected region of frustration may constitute apixel capable of external control.

BRIEF SUMMARY OF THE INVENTION

At a high level, this disclosure describes optical displaysincorporating or otherwise using backside reflection. More specifically,in certain embodiments, a flat panel or other TMOS display may presentpixels that are activated by violating the conditions for total internalreflection within a light guide or its light guidance substrate. Forexample, an optical component may include a light guide adapted toconduct light wherein at least some portion of the light guide isdeformable and an active layer disposed on the light guide whereby theactive layer selectively reflects light by deforming a first surface ofthe light guide such that light is ejected from a second surface of thelight guide. In certain situations, the deformable portion of the lightguide may be a deformable elastomer layer. The deformable elastomerlayer can then be disposed between the first surface of a light guidancesubstrate of the light guide and the active layer.

In another example, an optical display comprises a light guide adaptedto conduct light under conditions of total internal reflection, with atleast a portion of the light guide being deformable. An active layer isdisposed on the light guide whereby the active layer selectivelyreflects light by selectively deforming a first surface of the lightguide such that light is ejected from a second surface of the lightguide. The display also includes a light source—potentially capable ofoutputting alternating pulses of primary colored or infraredlight—coupled with the light guide.

In a further example, an optical display comprises a light guide adaptedto conduct light under conditions of total internal reflection where atleast a portion of the light guide is deformable. A plurality of modularactive layer disposed in an arrayed manner on a deformable surface ofthe light guide whereby the modular active layer reflects light byselectively deforming a first surface of the light guide such that lightis ejected from a second surface of the light guide. This display alsoincludes a light source—potentially capable of outputting alternatingpulses of primary colored or infrared light—coupled with the lightguide.

To control these example displays or components thereof, instructionsmay be executed as appropriate. The instructions may cause a lightsource to output alternating pulses of light through a light guideadapted to conduct light under conditions of total internal reflection,with at least a portion of the light guide being deformable. Theinstructions may (often concurrently) selectively apply an electrostaticfield to an active layer disposed on a first side of the light guide todeform a particular portion of the first surface of the light guide suchthat the light is ejected from a second surface of the light guide.

A method for fabricating such optical displays may include selecting alight guide adapted to conduct light under conditions of total internalreflection, with at least a portion of the light guide being deformable.The method may further include coupling a light source, capable ofoutputting alternating pulses of light, to the light guide and arranginga plurality of modules on the light guide. Each module could comprise anactive layer and a driving layer, with the active layer disposed on afirst surface of the light guide such that light is ejected from asecond surface of the light guide upon selective deformation of theactive layer by the driving layer.

The foregoing methods—as well as other disclosed example methods—may becomputer managed or implementable. For example, the display may includeprocessors or other control architecture that implements some or all ofthe example techniques. Put another way, some or all of these featuresor aspects may be further included or implemented in respectivesoftware. Generally, such features or aspects of these and otherembodiments are set forth in the accompanying drawings and thedescription below. For example, some of these embodiments may be able tolocally violate the conditions of total internal reflection on thesurface of the waveguide that is opposite (and typically parallel) tothe surface from which light is ejected. In this case, the optical pathbetween the viewer and the light ejected from the display can be lessobstructed, thereby resulting in a brighter, more efficient display.Indeed, a MEMS-based or other active layer may not be made of opticallytransparent materials since it will not lie within the optical path ofthe viewer. Therefore, a wider range of materials may be considered,which can result in cost reduction. Also, this may allow flat paneldisplays to be constructed of smaller modular components of fixed costthat have a more linear cost curve. This cost savings could make verylarge displays (e.g. optical display billboards) more affordable andeasier to realize.

Another advantage potentially provided by such backside reflection couldinclude a more parallel manufacturing or fabrication process. Forexample, the described displays could be manufactured with moreindependent, interchangeable parts that benefit from a parallelmanufacturing process. In other words, the interchangeable parts may befabricated independently and assembled into a final product, therebypossibly reducing production costs as well as the overall time ofproduction. Further, interchangeable parts can facilitate repair.

Of course, these example features are for illustration purposes only andsome or all may not be fully present (if at all) in certain embodiments.Other features, objects, and advantages will be apparent from thedescription and drawings and from the example claims.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. The novel features which are believed to be characteristic ofthe invention, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an example display according to certain embodimentsof the present disclosure;

FIG. 2 is a more detailed illustration of a portion of the (perhapslarge scale) display in FIG. 1 showing some of the exampleself-contained modules;

FIG. 3 provides a high level view of the three layers assembled to formthe portion of the display of FIG. 2;

FIGS. 4A-D are example views of the light guide described in FIG. 3, thestate of the light guide during pixel activation, and a magnification ofthe situs of such pixel activation;

FIGS. 5A-B illustrate example views of the active layer according tocertain embodiments of FIG. 3;

FIGS. 6A-B illustrate example views of the driving layer according tocertain embodiments of FIG. 3;

FIGS. 7A-C illustrate example views of a portion of the display in aquiescent state and with an activated pixel according to certainembodiments of the present disclosure;

FIGS. 8A-B illustrate various views of another example portion of thedisplay comprising an anisotropic conductive film adhesive (ACF) toactivate a pixel according to certain embodiments of the presentdisclosure;

FIG. 9 shows a side view of another example portion of the display wherea plurality of common conductors is disposed on the flexible membraneaccording to certain embodiments of the present disclosure;

FIGS. 10A-B illustrate various views of another example portion of thedisplay comprising a transparent common conductor disposed on adeformable elastomer layer according to certain embodiments of thepresent disclosure;

FIG. 11 shows a side view of another example portion of the displaywhere the flexible membrane is comprised of a material that expandsunder an electrostatic field, such as electroactive polymers (EAP), withan activated pixel according to certain embodiments of the presentdisclosure;

FIGS. 12A-D illustrate another example portion of the display,comprising pairs of pad electrodes disposed on a top surface of asubstrate, in the quiescent state and with a pixel activated accordingto certain embodiments of the present disclosure; and

FIGS. 13A-B illustrate an example portion of the display, in thequiescent state and with a pixel activated respectively, utilizing astandoff between two pixels according to certain embodiments of thepresent disclosure.

DETAILED DESCRIPTION OF THE INVENTION

At a high level, FIG. 1 illustrates an example optical display device100 that may utilize backside reflection as described herein. Generally,backside reflection indicates that the display 100 allows for thedeformation of a first surface of a light guide such that light isejected from a second surface of the light guide. In other words,backside may be used to indicate any side or other portion of the lightguide apart from that emitting the particular light. In someimplementations, this display device 100 may be a flat panel display forcomputers, cell phones and PDAs, televisions, automobiles, medical ordiagnostic applications, military and avionics, or in any other suitableapplication or system. For example, display 100 may be implemented in alaptop (or other handheld) computer because the potentialenergy-efficiency may extend the battery life. Also, display 100 may bemore sunlight readable with higher resolution. In another example,display 100 may display images up to three times higher in resolution,thereby enhancing diagnostic capabilities. This display 100 may also beoperable to provide a viewing angle greater than 170 degrees, therebygiving the viewer exceptional latitude in positioning or locating thedisplay 100. Moreover, these displays may be bendable (like fiber opticcable) with a radius of curvature of over 20 times the display'sthickness. In such an example, display 100 may be used in outdoorsystems because of its flexibility and ruggedness.

Generally, the present disclosure discusses an optical display 100 thatemits light by disposing guidance deforming components (such as anactive layer 300) on one surface of an optical waveguide (or lightguide) such that light is reflected or otherwise ejected from anothersurface. The deformation of the light guide frustrates total internalreflection causing light to be ejected locally at the surface opposingsome portion of each deformation. More specifically, by selectivelydeforming one surface of a light guidance substrate such that theconditions for total internal reflection within the light guidancesubstrate are locally violated, light within the light guidancesubstrate is reflected at these deformations at an angle sufficient toexit the light guide at another surface of the light guide.

As shown in FIG. 1, each of these deformations in display 100 mayrepresent a display pixel 120. A typical display 100 could contain anembedded matrix of over a million such pixels according to theresolution requirements or desires of a given application. In somecases, MEMS devices—whether microelectromechanical systems ornanoelectromechanical systems—are disposed at the location of each pixel120 to selectively violate the conditions for total internal reflectionon the deformable surface of the light guide 200. For example, theseexample pixels can be configured as a MEMS device using a parallel platecapacitor system that propels a deformable membrane between twodifferent positions and/or shapes. One position or shape corresponds toa quiescent, inactive state where FTIR does not occur due to inadequateproximity of the membrane to the waveguide. The other position or shapecorresponds to an active, coupled state where FTIR does occur due toadequate proximity. These two states correspond to off and on states forthe display pixel 120.

An aggregate MEMS-based structure may form an active layer 300 (shown inFIG. 3) that, when suitably configured, functions as a TMOS videodisplay capable of color generation, usually by exploiting fieldsequential color and pulse width modulation (PWM) techniques. Regardlessof the particular implementation, the active layer (300) may be disposedoutside the optical path of the viewer such that the light can ejectedfrom the surface of the light guide that is not the same side as eachrespective deformation. Consequently, the active layer 300 does not needto be transparent and may be comprised of cheaper or more resilientopaque materials. For example, when the “back” surface of the lightguide is actuated, light can be ejected from the “front” surface of thelight guide, as perceived by a viewer. Also, driving circuitry may bedisposed on the active layer 300 using any suitable circuit printingtechniques. Indeed, because it does not necessarily lie within theoptical path of the viewer, the active layer 300 may be designed orfabricated as a self-contained modular unit 150 that can containsdriving circuitry as appropriate. More specifically, as shown in FIG. 2,a rectangular array of such MEMS-based pixel regions 150, which areoften controlled by electrical/electronic components, can be fabricated“behind” the active surface of the planar waveguide. In this fashion, aplurality of such modular units 150 can be arrayed or otherwise coupledto a very large light guide 200 in such a manner that helps achieve aflat panel or other optical display of very large dimensions, such as inan optical billboard, highway sign, trade show signage and kiosks, andother large scale application. Moreover, since the active layer 300 canbe fabricated independent of the light guide, its fabrication is notdependent upon the final size of the light guide. Further, thesecomponents may be manufactured or distributed by multiple manufacturersand vendors without tight process control or compatibility concerns. Inother words, self contained modular units may be fabricated at any timefor multiple vendors or distributors and subsequently arrayed on thedesired light guide during final assembly. In addition, some of theseparts may be fabricated in a manner that is substantially independent ofone another and then assembled in a final assembly process. In somecircumstances, this enables a manufacturing process that is moreparallel, perhaps using multiple manufacturers. In this embodiment, noportion of the active layer 300 needs to be fabricated on the lightguide.

Disposed along at least one edge of the light guide 200 is a lightsource 110 capable of emitting pulses of light. This light source 110may be operable to emit visible light, infrared, or any other suitablelight wave. For example, an infrared lamp may be disposed next tocolored lamps. The sources are chosen to emit the primary colors ofvisible light to achieve the desired color gamut of the display.Typically the sources are red, green and blue light emitting diodes thatcan be temporally multiplexed to provide the familiar color gamut knownto color displays. In this example, short bursts of red, green and bluelight are emitted through the same dot so quickly that the eye also seesthem as a single color. In this case, different durations of red, greenand blue create different shades and hues. More specifically, theduration of the charge helps control the opening and closing of theparticular pixel. It is this duration that can determine the relativeintensity of the color. One frequency for a full cycle of suchalternations (red-green-blue) is typically 1/60 second. Thus everysecond, red, green and blue are flashed into the guidance substrate 60times each, meaning roughly 180 flashes total of all colors combined ina second. For example, to produce a white background, each appropriatepixel is open for the entire duration of the red, green and blue cycles.To produce black text on the white background, each pixel representing aletter (or portion thereof) is closed for the entire duration of eachcycle. In another example, to produce fifty percent gray, eachrespective pixel is open for 50 percent of each red, green and bluecycle. In yet another example, to produce a blue background, eachappropriate pixel is closed during red and green cycles, but open duringthe blue cycle. The shade of blue is determined by the percentage of theblue cycle that the pixel is open (perhaps 10%=deep blue and 100%=brightblue). In short, each pixel can be left open for different percentagesof the red, green and blue cycles to produce millions of differentcolors and shades of gray, a technique commonly referred to as pulsewidth modulation (PWM). But it will be understood that optical display100 may be used for any suitable purpose and any light and/or color maybe used. For example, an infrared light source 110 can be utilized ifsuch an application is appropriate. In this example, a color display 100could be converted to an infrared display 100 by shutting down thered-green-blue cycle (or removing the ROB source) and coupling acontinuous infrared source to the light guide.

For a color display using time multiplexed optical shuttering (TMOS),the light source 110 comprises a plurality of sources capable ofoutputting alternating pulses of monochromatic light, such as lightemitting diodes (LEDs). To increase distribution and mixture oftristimulus light within the light guide 200, a linearly arrayedconcatenation of LEDs may be used. The individual LEDs may be simplex ortriplex structures based, at least in part, on an application'sdimensional and power dissipation considerations. A simplex LED is adiscrete element that emits only one primary color. A triplex LEDcombines all three tristimulus primaries within a more unitary package(where the respective junctions may even share a common reflector andpotting compound). The mounting for these linear arrays may also serveas the primary heat sink for these power-intensive illuminating systems.

Often, the geometry of the encapsulating structure in which the junctionis embedded helps determine the optimal separation between the lightguide 200 insertion face and the light source 110. The consequence ofthis physical separation is the trigonometric restriction on the anglesof incidence of light encountering the insertion face. Moreover, Fresnelinsertion losses apply to light entering light guide 200 from thesurrounding air: maximum insertion occurs when the rays enter normal tothe insertion face, while insertion becomes increasingly attenuated forrays at glancing angles. Typically, these issues do not arise forarchitectures that actually embed the light source 110 within lightguide 200 or otherwise avoid ray transit through air prior to lighttravel within light guide 200. For example, the LEDs may be directlycoupled to the light guide 200 by means of a silicone bridge, therebyimproving the range of useful angles injected into light guide 200. Thecoupling of light at the interface of the actuated active layer 300 andlight guide 200 may be based on geometric considerations involving thenature of the two surfaces making contact. For example, Parylene (whichmay be prepared by deposition on silicon wafers) may yield good opticalcoupling due to reduced surface roughness and better contact intimacy.In another example, materials that are not flat (such as latex) canstill couple well under even slight pressure, since the compliance ofthe elastic material causes the latex to conform to the surface of thelight guide 200, thereby providing intimacy of contact without benefitof an initially high surface flatness specification. In fact, ahybridized structure where latex coating is added onto a membrane may beused. In some cases, intimacy of contact over a sufficiently large (>3λ)area may provide a sufficient coupling.

FIG. 3 provides a high level view of the three layers assembled to formone portion of the display. The light guide 200, active layer 300, anddriving layer 400 can all be manufactured separately and in parallel.Each of the three layers can be assembled together at the end of theproduction process to yield a completed display 100. In fact, each layermay not be manufactured to the same planar dimensions, which can bevaried for each part to optimize cost and performance criteria. Forexample, since the drive circuit 422 for the driving layer 400 can beprinted on the back of the substrate 420, the driving layer 400 whencombined with an active layer 300 can function as a self-containedmodular unit 150.

FIG. 4A shows the light guide 200, often comprising a generally planarlight guidance substrate 201. The light guidance substrate 201 isnormally manufactured using an optically transparent material of highrefractive index such as glass or plastic. For example, high qualityoptical glasses may be used. In another example, certain polymersubstrates may be selected because of lower densities (and acorresponding lower weight per screen), lower cost, and superiormechanical robustness. More specifically, light guide substrate 201 mayalso be fabricated using any number of other polycarbonates withsufficient clarity, perfluoropolymers configured to achieve some paritywith optical glass, hollow waveguides, or any other suitable materialsor components. FIG. 4A further depicts a light ray 105 injected into thelight guide 200 from the light source 110 and channeled within the lightguide 200 via total internal reflection. More specifically, lightentering the light guidance substrate 201 from the light source 110 isrefracted such that the incident light experiences total internalreflection within the light guidance substrate 201. In some cases, theside surfaces of the light guide may be mirrored 204 to prevent lightfrom escaping at the edges. The light guidance substrate 201 is composedof a rigid, transparent material of optical quality. In this illustratedembodiment, a deformable elastomer layer 202 is disposed upon a firstsurface of the light guidance substrate 201. The deformable elastomerlayer 202 is normally optically transparent and its index of refractionis sufficiently matched to the index of refraction of the light guidancesubstrate 201 so that there is no substantial optical boundary betweenthe deformable elastomer layer 202 and the light guidance substrate 201.In many cases, the two structures function as a single light guide 200such that conditions for total internal reflection may exist within theentire structure. The light guide 200 is designed to channel or guidelight received from the light source 110 under conditions that satisfytotal internal reflection. For example, the light guide 200 may havemirrored surfaces 204 on sides against which a light source 110 is notdisposed, which may help minimize optical losses.

FIG. 4B shows an alternative embodiment of a light guide 200. In thissituation, the illustrated portion of light guidance substrate 201 iscomprised of a deformable elastomer of high refractive index.Accordingly, there may be no need for a deformable elastomer layer to bedisposed upon the light guidance substrate 201. Any surface of the lightguide 200 is thus capable of undergoing selective local deformation.

FIG. 4C shows the state of the light guide 200 during pixel activation.Prior to pixel activation, the light rays 105 within the light guide 200typically do not strike either large surface of the light guide 200 atan angle of incidence great enough to overcome total internalreflection. The deformable elastomer layer 202 has been pushed upward atthe surface by the active portion of the flexible membrane 110 (notshown) resulting in a deformation. The light rays 105 within the lightguide 200 contact the boundary of the deformable elastomer layer 202 atthe situs of the deformation. That light is reflected at an anglesufficient to exit the light guide 200 at the surface opposite to thedeformation, which is normally the so-called front or viewable surfaceof the display 100.

FIG. 4D shows a magnified view of the light guide 200 near the situs ofpixel activation. The scale is exaggerated to more clearly show thefeatures. In embodiments that include a coating of small asperities 314disposed on the surface of the common conductor 312, these asperitiesensure multiple reflection points within the pixel area to maximizelight output. These reflection points are caused when the surface of thedeformable elastomer layer 202 is not smoothly deformed. The small 314asperities cause multiple surface deformations across the entire pixelarea as opposed to only a single global deformation for each pixel.

The selective deformation of a first surface of the light guide 200results in light being locally ejected from a second surface of thelight guide 200. Every component required to activate the pixel, inrelation to the viewer, lies behind the surface from which light isreflected out of the light guide 200. Except for any protective coatingsused in commercial applications, the optical path between the viewer andthe point at which light is ejected from the light guide 200 isrelatively unobstructed. More specifically, there may be no transparentconductors, thin film transistors, cladding layers, and such to causeloss. Furthermore, there is no need for the materials in the activelayer 300 or driving layer 400 to be optically transparent. In fact, thecommon conductor 312 is often dark in color and non-reflective. Thisenables the substrate 420 to be made of an opaque material such as awafer or printed circuit board. The drive circuit 422 can be disposed onthe back of the substrate 420 using common, low-cost circuit boardmanufacturing techniques.

FIG. 5A shows the active layer 300 of the display. The words top andbottom are used herein only in reference to the orientation of thefigures as shown. The active layer 300 is comprised of a flexiblemembrane 310. In the preferred embodiment, the flexible membrane 310 iscomposed of a material or device that changes position and/or shape inresponse to an applied electrostatic field and in a manner that iswell-suited to external control. Such materials include electro-activepolymers like polyvinylidine difluoride (PVDF), metallized piezoelectricfilms and a wide range of MEMS devices that can produce the requiredlocalized dimensional change. This disclosure contemplates otherembodiments of selective localized activation or deformation well-suitedto external control that respond to electrostatic, electromagnetic,electrochemical or thermal stimuli.

Pixel conductors 311 are patterned on the bottom surface of the flexiblemembrane 310. An opaque common conductor 312 is disposed on the topsurface of the flexible membrane 310. The common conductor 312 istypically non-reflective so that light is not coupled into the activelayer 300 when it comes into contact with the light guide 200. Thesurface of the common conductor 312 is preferably black in color toimprove the contrast ratio of the emitted light, since that is what theviewer sees when the pixel is off. The surface of the common conductor312 may be coated with a layer of small asperities 314, such as glassbeads. A through-hole conductor 313 extends from common conductor 312 onthe top of the flexible membrane 310 to the bottom surface for thepurpose of providing a contact point for the common conductor and thedriving layer 400 shown in FIG. 6. FIG. 5B shows a bottom view of theactive layer 300. Pixel conductors 311 are patterned on the bottom ofthe flexible membrane 310 at each situs where a display pixel islocated.

FIG. 6A shows the driving layer 400. The driving layer 400 is comprisedof a substrate 420, such as a silicon wafer, flex circuit, or printedcircuit board. The driving layer 400 may be controlled by a processor orother control architecture (such as a video converter and fieldsequential color converter) that executes instructions and manipulatesdata to perform the operations of display 100. These control componentsmay include, for example, a central processing unit (CPU), anapplication specific integrated circuit (ASIC) or a field-programmablegate array (FPGA). The display 100 could behave as a large dynamic RAMchip and be driven directly by video RAM in one-to-one correlation underan extremely rapid refresh regimen. In some systems, converters could beutilized with the present invention to permit compatibility withconventional television or with high definition television (HDTV).Moreover, the control components may collectively or individuallyexecute software operable to manage the various layers and displaycomponents. For example, these instructions may be written or describedin any appropriate computer language including C, C++, assembler, PerI,any suitable scripting language, or any combination thereof. Regardlessof the particular implementation, “software” may include software,firmware, wired or programmed hardware, or any combination thereof asappropriate.

Returning to the illustrated embodiment, driving layer 400 may include adrive circuit 422 that can be placed on the bottom side of the substrate420. In the illustrated example, a plurality of pad electrodes 421 isdisposed on the top surface of the substrate 420. Each pad electrode 421is disposed on the substrate 420 such that each pad electrode 421 cancorrespond to a pixel conductor 311 on the active layer 300. When theactive layer 300 is brought into contact with the driving layer 400,each pad electrode 421 comes into contact with its corresponding pixelconductor 311 making an electrical connection. The through-holeconductor 313 will come into contact with a pad electrode 421 thatdrives the common conductor 312. The thickness of the pad electrodes 421and any adhesive are typically sufficient to provide a standoff betweenthe driving layer 400 and the active layer 300. FIG. 6B shows a top viewof the driving layer 400.

FIG. 7A shows the three layers (light guide 200, active layer 300 anddriving layer 400) assembled to form any portion of display 100, such asmodule 150. The active layer 300 is disposed such that the commonconductor 312 is brought into close proximity to (but normally not incontact with) the surface of the deformable elastomer layer 202 of thelight guide 200. With regard to the example shown of FIG. 4B, eithersurface of the light guidance substrate 201 may be brought into closeproximity with the active layer 300. Put another way, the “bottom” orthe “top” of the light guidance substrate 201 may be immaterial in thelong dimension. In some embodiments, the driving layer 400 is affixed tothe active layer 300 such that the pad electrodes 421 line up with thepixel conductors 311. FIGS. 7B-C illustrate various materials thatbuckle or bulge under the influence of an electrostatic field, thoughmaterials that exhibit similar behavior under the influence of otherstimuli may also be utilized.

More particularly, FIG. 7B illustrates a material that expandspredominantly in the horizontal direction (causing the flexible membrane310 to buckle), while FIG. 7C illustrates a material that expandspredominantly in the vertical direction (causing the flexible membrane310 to bulge). FIG. 7B shows a display with an activated pixel. In thepreferred embodiment, a pixel is activated by placing an electrostaticpotential between the common conductor 312 and the pixel conductor 311corresponding to the pixel that is to be activated. The flexiblemembrane 310 changes shape in a desired manner in response to theapplied electrostatic field. This causes an upward local deformation ofthe flexible membrane 310 at the situs of the pixel being activated. Asthe flexible membrane 310 pushes upward, it contacts the deformableelastomer layer 202 of the light guide 200. The deformable elastomerlayer 202 is mechanically pushed upward in a corresponding manner. Thischanges the geometry of the deformable elastomer layer 202, defeatingthe conditions for total internal reflection within the light guide 200.The deformation shown in FIG. 8 is more typical of a material thatexpands predominantly in the horizontal direction, causing the flexiblemembrane 310 to buckle. FIG. 7C shows the deformation of a material thatexpands predominantly in vertical direction, causing the flexiblemembrane 310 to bulge. An optional non-conductive shim 725 may bedisposed between the substrate 420 and the pixel conductor 311 tofurther control the deformation of the flexible membrane 310. Thenon-conductive shim forces the flexible membrane 310 to bulge or bucklein the direction of the light guide 200 and not back toward the drivinglayer.

FIG. 8A shows another embodiment of the portion of the display 100, suchas a module 150. In this case, anisotropic conductive film adhesive(ACF) 850 is used to selectively activate a particular pixel. ACF 850can be a thermoset epoxy system that is generally conductive in onedimension and non-conductive in others. An ACF layer of any suitablethickness is disposed between the active layer 300 and the driving layer400. The pixel is activated by means of a pixel electrode 851 and theexcitation of ACF 850 that lies directly above it. The dimensions ofpixel electrode 851 are often matched to the size of a display pixel.Pixel conductors 311 may not be necessary since their electricalfunction has been replaced by the layer of ACF 850.

FIG. 8B shows the activation of a pixel shown in FIG. 8A slightlymagnified. In this case, pixel activation is achieved via a conductivepath with an electrical connection between the ACF 850 and the pixelelectrode 851. Accordingly, ACF 850 is conductive only in the verticaldirection and in the region bounded by the horizontally planardimensions of the pixel electrode 851. This electrical connectioncreates a parallel plate capacitor between the shaded regions of ACF 850and the common conductor 312 (except in the region where the throughhole conductor 313 connects the ACF 850 to the common conductor 312).Upon charging, Coulomb attraction sets up an electrostatic field acrossthe capacitor that deforms the flexible membrane 310.

FIG. 9 shows another embodiment of the portion of the display 100, suchas a module 150. In this example, the common conductor 312 on top of theflexible membrane 310 in FIG. 3 is replaced with individual pixelconductors 940. This similarly creates a localized parallel platecapacitor at the situs of each pixel. Each individual pixel conductor940 is connected to the driving layer 400 by means of a through-holeconductor 313. Additional pad conductors 421 are added to the substrate420 of the driving layer to electrically connect each through-holeconductor 313.

FIG. 10A shows another embodiment of the portion of the display 100,such as a module 150, wherein a transparent common conductor 1001 isdisposed on the deformable elastomer layer 202. The transparent commonconductor 1001 can be made from a material such as indium tin oxide. Anindividual pixel conductor 940 is disposed on top of the flexiblemembrane 310 and electrically connected to the substrate 420 by means ofa through-hole conductor 313 and pad conductor 421. The individual pixelconductors 940 may have a coating of small asperities 314 on the topsurface. A parallel plate capacitor is set up between the transparentcommon conductor 1001 and each individual pixel conductor 940. When thelight guidance substrate 201 is deformable, as in FIG. 4B, thisalternative embodiment can be realized by disposing the transparentcommon conductor on the top surface of the light guidance substrate 201.Two factors for consideration may be the thickness of the light guidancesubstrate 201 and the concomitant voltage required to activate thepixel. Often as thickness increases, so does the voltage required toactivate the pixel.

FIG. 10B shows the embodiment in FIG. 10A where the pixel 120 isactivated by electrostatic attraction. hen a charge is placed onindividual pixel conductor 940, it is drawn by Coulomb attraction towardthe transparent common conductor 1001. The activated individual pixelconductor 940 presses upward into the deformable elastomer layer 202creating a localized deformation at the situs of the pixel. Lightreflects off of this deformation and is ejected from the light guidancesubstrate 201.

FIG. 11 shows another embodiment of the portion of the display 100, suchas a module 150, wherein the deformable elastomer layer 202 is comprisedof a material that expands under the influence of an electrostaticfield, such as electroactive polymers (EAP). A transparent commonconductor 1001 is disposed on the deformable elastomer layer 202. Theneed for a flexible membrane is eliminated. The pixel conductors 940 aredisposed on the top surface of the substrate 420. This can occasionallybe done rather inexpensively using, for example, traditional circuitboard printing. The top of each individual pixel conductor 940 may becoated with small asperities 314. A parallel plate capacitor is set upbetween the transparent common conductor 1001 and each pixel conductor940. A pixel is activated by placing a charge on the pixel conductor940. An electrostatic field is set up between the transparent commonconductor 1001 and the individual pixel conductor 940. Under theinfluence of this field, the deformable elastomer layer 202 composed ofEAP expands downward, pressing against the pixel conductor 940 and thesmall asperities 314 that coat its surface. This creates a localizeddeformation at the situs of the pixel. Light reflects off of thisdeformation and is ejected from the light guidance substrate 201.

FIGS. 12A-D show another embodiment of the portion of the display 100,such as a module 150. In the illustrated embodiment, pairs of padelectrodes 621 and 622 are disposed on the top surface of a substrate420. Comb-like coplanar pixel conductors 511 and 512 are also disposedin an interdigitated manner on the “bottom” surface of the flexiblemembrane 310. Disposing a common conductor in another plane may not benecessary to actuate the flexible membrane 310. Each pixel conductor 511and 512 comprises an electrical pole. The active layer 500 and thedriving layer 600 are disposed so that the pad electrodes 621 makeelectrical contact with the pixel conductors 511 and pad electrodes 622make electrical contact with the pixel conductors 512. The flexiblemembrane 310 is composed of a material that expands under the influenceof an electric field, such as EAP. The desired pixel 120 is activated byplacing an electric potential between pixel conductor 511 and pixelconductor 512. This causes the flexible membrane 310 to expand, which inturn causes it to buckle upward. The flexible membrane 310 presses intothe deformable elastomer layer 202 forming a deformation at the situs ofthe pixel, as shown in FIG. 12D. Small asperities 314 may be disposed onthe top surface of the flexible membrane to provide multiple reflectionpoints. The top surface of the flexible membrane is normally opaque andnon-reflective to provide adequate contrast.

FIGS. 13A-B illustrate an example portion of the display, in thequiescent state and with a pixel activated respectively, utilizing astandoff 1034 between two pixels according to certain embodiments of thepresent disclosure. Standoff 1304 may comprise any suitable materialssuch as, for example, silicone, parylene or polyethylene terephthalate.Generally, use of this standoff 1304 between pixels may help mitigatepixel cross talk, which may occur when light is ejected from a pixel1302 unintentionally due to actuation of an adjacent pixel 1301.Specifically, in some cases, the active layer 300 may bend sharplyupward at the margin of a given pixel area, so that it is in fullcontact with the light guide within the area of the pixel 1301 and notin contact in the surrounding areas outside the particular pixel. Suchsharpness of this bending is typically a material property. Thus, toprevent the selectively deformed portion of the active layer 300 fromcoming into contact with the light guide 200 in the area of an adjacentpixel, the effective size of the pixel can be reduced (or the spacebetween pixels 1303 must be increased). Further, the use of the standoff1304 between pixels helps enable a “sharper” deformation in the activelayer 300, thereby possibly reducing the unused space between pixels1303. In certain embodiments, the light guide 200 may couple into thestandoff 1304 when they come into contact, as depicted by light ray 107,upon pixel activation. This can introduce noise into the display and mayreduce the contrast ratio of the display. But, in certain cases, lightmay not effectively couple into a material that has a surface roughnessexceeding 100 nanometers, as shown at 1305. Accordingly, if the surfaceof the standoff that contacts the light guide has a roughness greaterthan 100 nanometers, then light from the light guide 200 may not followthe path of light ray 107 and noise further reduced.

It will be understood that many of the preceding figures are not drawnto scale in an effort to aid the reader. Further, the precedingdescription discusses example techniques. But this disclosurecontemplates using any suitable technique for performing these and othersimilar tasks. Accordingly, many of the steps may take placesimultaneously and/or in different orders than as shown. Moreover,manufacturers or other parties may use methods with additional steps,fewer steps, and/or different steps, so long as the methods remainappropriate. While various embodiments have been described, it will beunderstood that various modifications may be made without departing fromthe spirit and scope of the disclosure. For example, while the terms“bottom” and “top” have been used to more easily describe the display,the display may be oriented in any suitable direction. Indeed, aparticular deformable surface of the light guide may not be directlyopposite (or parallel to) the surface emitting the light as appropriate.Accordingly, other embodiments are within the scope of the followingclaims.

1. An optical component comprising: a light guide adapted to conductlight under conditions of total internal reflection, at least a portionof the light guide being deformable; and an active layer, disposed onthe light guide, that selectively reflects light by deforming a firstsurface of the light guide such that the light is ejected from someportion of a second surface of the light guide.